Conversion of hydrocarbon oils



April 4, 1939. J. D. SEGUY CONVERSION OF HYDROCARBQN OILS Fiied April 25, 1954 INVEN OR JEAN DE A '5 E SEGUY TORNEY Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE CONVERSION OF HYDROCARBON OILS Application April 23, 1934, Serial No. 721,905

3 Claims.

This invention particularly refers to an improved process and apparatus forthe pyrolytic conversion of hydrocarbon oils of a relatively high-boiling nature for the production of high 5 yields of desirable low-boiling products, such as motor fuel of high antiknock value, of the character wherein the intermediate conversion products of the process are separated into selected relatively low-boiling and high-boiling oils each 0 of which are subjected to the independently controlled conversion conditions most suitable for that particular type of oil.

The present invention employs twoindependently controlled but interdependent and cooperative cracking units, one of which is specially adapted to the conversion of relatively heavy or high-boiling oils at relatively low temperatures and pressure while the other is particularly suitable for the conversion of relatively light or lowboiling oils at higher temperatures and pressures, each unit being operated for the production of maximum yields of light distillate products boiling within the range of motor fuel. The intermediate conversion products heavier than gasoline (reflux condensate) produced in each unit are separated into selected relatively low-boiling and high-boiling fractions, the high-boiling fractions from each unit being supplied for further conversion to the heating coil of the unit specially adapted to the treatment of high-boiling oils while the low-boiling reflux condensate fractions having boiling characteristics similar to kerosene or pressure distillate bottoms from each unit are supplied for further conversion to the heating coil of the unit particularly adapted to the treatment of relatively low-boiling oils.

One specific embodiment of the present invention may comprise subjecting hydrocarbon oil of relatively high-boiling characteristics to conversion temperature at superatmospheric pressure in a heating coil, introducing heated products into an enlarged reaction chamber, also maintained at superatmospheric pressure, wherein the vaporous and non-vaporous residual conversion products separate, subjecting vaporous products from the reaction chamber to fractionation whereby their high-boiling, insuificiently converted components are condensed as primary reflux condensate having boiling range characteristics corresponding to gas oil, subjecting the remaining vaporous products, corresponding to pressure distillate, to further fractionation whereby the lower boiling, insufiiciently converted components, comprising pressure distillate bottoms, are condensed as see- 5" ondary reflux condensate, subjecting the vaporous products from the final stage of fractionation, preferably having an end-boiling point corresponding to that of motor fuel, to condensation, recovering the resulting motor fuel, returning the primary reflux condensate, corresponding, for ex- 5 ample, to gas oil, to the heating coil for further conversion, subjecting the secondary reflux condensate, such as pressure distillate bottoms, to independently controlled conversion conditions of elevated temperature and superatmospheric pres- 10 sure, higher than the temperature and pressure conditions to which the higher-boiling oils, comprising the primary reflux condensate, are subjected, in a separate heating coil and communicating reaction chamber, withdrawing the total 5 conversion products, in commingled state, from the reaction chamber and introducing the same into a reduced pressure vaporizing chamber, wherein vaporous conversion products are separated from residual liquid, withdrawing the latter 20 from the system, subjecting the vaporous conversion products of this stage of the system tofractionation, whereby their high-boiling, insuificiently converted components are condensed and separated into primary and secondary reflux 25 condensate, comprising, respectively, materials corresponding to gas oil and materials corresponding to naphtha and/or kerosene, returning said primary reflux condensate to the first mentioned heating coil for further conversion at rela- 30 tively low temperature and pressure, returning the secondary reflux condensate to said separate heating coil for further conversion under higher temperature and pressure conditions, subjecting the vaporous products from the last mentioned 35 fractionating stage, preferably corresponding to motor fuel, to condensation and collecting the resulting distillate. It is also within'the scope of the invention, when desired, to subject residual liquid conversion products from the first men- 40 tioned reaction chamber, when such materials are produced in this zone, to flash distillation, the residual liquid remaining unvaporized after such treatment being withdrawn from the system while the evolved flashed vapors are separated into rel- 5 atively low-boiling and high-boiling components, the latter being returned to the first mentioned heating coil for further conversion and the former supplied for further conversion to said separate heating coil. 7 50 Raw oil charging stock of relatively high-boiling characteristics may be supplied to the heating coil of the cracking unit devoted to the treatment of relatively high-boiling oils or to any suitable intermediate point in the system wherefrom it may be returned to this heating coil. Charging stock of a relatively low-boiling nature may be supplied to the heating coil of the cracking unit devoted to the treatment of relatively low-boiling oils or to any suitable intermediate point in the system wherefrom it may be returned to this heating coil. When a charging stock of relatively wide boiling range is employed it is preferably supplied to a suitable intermediate point or points in either or both of the cracking units wherein it may be separated into selected relatively low-boiling fractions, such as kerosene or naphtha, for example, and high-boiling fractions which are returned, respectively, to the heating coil devoted to the conversion of these fractions, as above described.

The accompanying diagrammatic drawing illustrates one specific form of apparatus embodying the features of the present invention. Referring to the drawing, heating coil I is located within a furnace 2 of any suitable form by means of which the required heat is supplied to the oil passing. through the heating coil to bring it to the desired conversion temperature preferably at a substantial superatmospheric pressure. The streamof heated oil is discharged from heating coil I through line 3 and valve 4 into reaction chamber 5, which is preferably insulated and maintained at a substantial superatmospheric pressure.

Conversion of the oil continues in the reaction chamber and the total conversion products are withdrawn in commingled state from the lower portion of chamber 5, passing through line 6 and valve 1 into vaporizing chamber 8, which is preferably maintained at a substantially reduced pressure relative to that employed in the reaction chamber. Vapors separate from non-vaporous residual liquid in chamber 8 and the residual liquid remaining unvaporized in this zone is withdrawn therefrom through line 9 and valve ID to cooling and storage or to any desired further treatment. The vaporous conversion products pass from the upper portion of chamber 8 through line H and valve [2 to fractionator I3.

Uncondensed vapors of the desired end-boiling point pass from the upper portion of column I3 through line l5 and valve l6 to further fractionation in column 4. A relatively high-boiling or primary reflux condensate, preferably corresponding in initial boiling point to gas oil, is collected in the lower portion of column l3 and a secondary reflux condensate of relatively low-boiling characteristics, such as kerosene or naphtha, for example is recovered from the lower portion of column |4.

Fractionated vapors of the desired end-boiling point, preferably corresponding to motor fuel, are withdrawn, together with uncondensable gas, from the upper portion of fractionator l4 through line I! and valve I8, to be subjected to condensation and cooling in condenser IS. The resulting motor fuel and uncondensable gas passes through line 20 and valve 2| to collection and separation in receiver 22. Uncondensable gas may be released from the receiver through line 23 and valve 24. The motor fuel may be withdrawn from the receiver through line 25 and valve 26 to storage or to any desired further treatment.

The relatively low-boiling reflux condensate, corresponding to kerosene or naphtha, for example, is withdrawn from the lower portion of fractionator l4 through line 21 and valve 28 to pump 29 by means of which it is returned through line 3!] and valve 3| to further conversion in heating coil Reflux condensate of relatively high-boiling characteristics, corresponding to gas oil, for example, is withdrawn from the lower portion of fractionator 3 through line 32 and valve 33 to pump 34, by means of which it is supplied through line 35, valve 36 and line 53 to further conversion in heating coil 31, wherein it is subjected to lower temperature and pressure conditions than those employed in heating coil l, by means of heat supplied from a suitable furnace 38, of any suitable form. The stream of heated oil is discharged from heating coil 37, preferably at a substantial superatmospheric pressure, through line 39 and valve 40 into reaction chamber 4|.

Chamber 4| is preferably insulated and maintained at a substantial superatmospheric pressure. Conversion of the heated products supplied to the reaction chamber from heating coil 31 may continue therein. Chamber 4| may be operated for the production of either liquid residue or coke, the residual product in either case being separated in chamber 4| from the vaporous conversion products. When the process is operated for the production of coke as the residual product of this stage of the operation it may be allowed to accumulate within chamber 4| to be removed therefrom in any suitable well known manner after the operation of the chamber is completed. When desired, a plurality of coking chambers, similar to chamber 4| but not shown in the drawing, may be employed and may be either simultaneously operated or, preferably, are alternately operated, cleaned and prepared for further operation so that the continuity of the operation is independent of the capacity of the coking chamber. When a liquid residual product is produced in chamber 4| it may be withdrawn, for example, from the lower portion of this zone through line 42 and valve 43 to cooling and storage or to any desired further treatment. One method of such further treatment which is within the scope of the present invention will be later more fully described. The vaporous conversion products pass from the upper portion of chamber 4| through line 44 and valve 45 to fractionation in fractionator 46.

Fractionated vapors of the desired end-boiling point, preferably lighter than gas oil, pass from the upper portion of fractionator 46 through line 48 and valve 49 to further fractionation in fractionator 41. A relatively high-boiling or primary reflux condensate, corresponding for example to gas oil, is recovered in fractionator 46 and a relatively low-boiling or secondary reflux condensate, corresponding, for example, to pressure distillate bottoms, is recovered from the remaining fractionated vapors in fractionator 41.

The primary reflux condensate recovered in column 46 may be withdrawn from the lower portion of this zone through line 56 and valve 5| to pump 52 by means of which it is returned through line 53 and valve 54 to further conversion in heating coil 37, together with primary reflux condensate from fractionator l3, supplied to this zone as already described.

The secondary reflux condensate formed in fractionator 4?, may be withdrawn from the lower portion of the column through line 55 and valve 56 to pump 5'! by means of which it is supplied, in the case illustrated, through line 58, valve 59, line 60 and valve 6| to fractionator l3, to serve as a cooling and refluxing medium in this zone to assist fractionationof the vapors by directly commingling therewith. The secondary reflux condensate from fractionator 41, thus supplied to fractionator I3, is subjected to vaporization in this zone by direct contact with the relatively hot vapors undergoing fractionation and passes with the uncondensed vapors from column l3 through line I5 and valve I6 to further fractionation in fractionator I4 wherein it is condensed with the secondary reflux condensate formed in this zone, to be returned therefrom to further conversion in heating coil I, in the manner previously described. It is, of course, also Within the scope of the invention, although not illustrated, to supply a regulated portion or all of the secondary reflux condensate from fractionator 41 direct to heating coil I.

Fractionated vapors of the desired end-boiling point, preferably corresponding to motor fuel, are withdrawn, together with uncondensable gas, from the upper portion of fractionator 41 through line 62 and valve 63 to be subjected to condensation and cooling in condenser 64. The resulting distillate and gas passes through line 65 and valve 66 to collection and separation in receiver 61. Uncondensable gas may be released from the receiver through line 68 and valve 69. Distillate may be withdrawn from receiver 6'! through line 10 and valve II to storage or to any desired further treatment.

It is within the scope of the present invention, as previously mentioned, to subject residual liquid conversion products from chamber 4| to further treatment within the system. As an example of one specific method and means of such further treatment, which is within the scope of the invention, all or a regulated portion of the liquid residue from chamber 4I may be diverted from line 42 through line 72 and valve 13 into flash distilling chamber I4, which is operated at a substantially reduced pressure relative to that employed in chamber 4|, by means of which appreciable further vaporization of the residual liquid is accomplished. The residual liquid remaining unvaporized in chamber "I4 may be withdrawn therefrom through line I5 and valve 16 to cooling and storage or elsewhere, as desired. The vapors evolved in chamber 14 pass, in the case illustrated, from the upper portion thereof through line "I? and valve I8 to fractionation in fractionator 19.

The components of the vaporous products supplied to fractionator I9, approximately corresponding in boiling characteristics to the primary reflux condensate recovered in fractionators I3 and 46, are condensed as flash condensate. This material may be withdrawn from the lower portion of column I9 through line and valve 8| to pump 82, wherefrom it is fed through line 83 to be returned to heating coil 3! for further conversion, being supplied, in the case illustrated, either through valve 84 in line 83 and through line 53 direct to heating coil 31 or from line 83 through line 85 and valve 88 into fractionator 46, toserve as a cooling and refluxing medium and to be returned therefrom, together with the reflux con densate formed in this zone, to heating coil 31, in the manner previously described.

The components of the vapors evolved in chamber 14 remaining uncondensed in fractionator I9, including, primarily, materials boiling within the range of the secondary reflux condensate formed in fractionators I 4 and 41, as well as any lower boiling materials, are withdrawn, together with uncondensable gas, from the upper portion of fractionator I9 through line 81 and valve 88 to be subjected to condensation and cooling in condenser 89, wherefrom the resulting distillate and gas passes through line 90 and valve 9| to collection and separation in receiver 92. Uncondensable gas may be released from the receiver through line 93 and valve 94. All or 'a regulated portion of the distillate may be withdrawn from receiver 92 through line 95 and valve 96 to storage or elsewhere, as desired. Preferably, however, all or a regulated portion of the distillate collected in receiver 92 is withdrawn therefrom through line 91 and valve 98 to pump 99, by means of which it is fed, in the case illustrated, through line I00, valve IOI, line 60 and valve BI into fractionator i 3, together with the secondary reflux condensate from fractionator 41. It is also within the scope of the present invention, particularly in case the flash distillate collected in receiver 92 comprises or contains a substantial proportion of materials within the boiling range of motor fuel but ofpoor antiknock value, to return the distillate from receiver 92, by well known means, not illustrated, direct to heating coil I, whereby the characteristics of the motor fuel components of the distillate may be materially improved, particularly with respect to their antiknock value, under the conversion conditions employed in this zone.

When a hydrocarbon oil charging stock of relatively high-boiling characteristics or of relatively wide boiling range is. employed it may be supplied through line I02 and valve I03 to pump I04 wherefrom it is fed through line- I05 and may be directed, all or in part, either through line I 06 and valve I 07 into fractionator I9 or through line I08, line I09, valve H0 and line I2 into flash distilling chamber I4, or from line I08 through line III and valve II2 into the lower portion of reaction chamber M. It is also within the scope of the invention, although not illustrated in the drawing, to supply charging stock of relatively high-boiling characteristics or charging stock of relatively wide boiling range either to fractionator I3 or to chamber 8 or to the lower portion of chamber 5, or the charging stock supplied to pump I04 may be fed to the system in any desired combination of the manners described. Charging stock of relatively high-boiling characteristics may also, when desired, be fed from pump I04 through lines I05, I08 and valve II 3 direct to heating coil 31.

When charging stock of relatively low-boiling characteristics is employed it may be supplied through line H4 and valve II5 to pump II 6 to be fed therefrom through line H1 and supplied, all or in part, either through line H8 and valve 1 I9 to fractionator I4 or through line I20, valve I2I and line 60 to fractionator I3, or relatively low-boiling charging stock may be supplied, by well known means, not illustrated, either to fractionator 46 or to fractionator 41 or to fractionator I9, or it may be supplied to the system in any combination of the manners described.

It is, of course, within the scope of the invention to employ both low-boiling and high-boiling charging stocks or to employ either or both in combination with a charging stock of relatively wide boiling range, although means for supplying more than twocharging stocks to the system separately are not illustrated.

It will be understood that the invention is not limited to the specific form of apparatus illustrated and above described nor to the specific flow shown. As an example of some of the many modifications possible within the scope of the present invention, a single fractionator may be employed instead of employing two fractionators in series such as fractionators I3 and I4 and/or fractionators 46 and 41, in which case high-boiling fractions of the reflux condensate may be withdrawn from the lower portion of the fractionator, to be returned to heating coil 31, while selected low-boiling fractions of the reflux condensate are withdrawn from any suitable intermediate point or plurality of points in the fractionator, to be returned to heating coil l for further conversion. Preferably a light distillate product of motor fuel boiling range is separately recovered from each of the two separate cracking stages of the system, since the cracking unit devoted to the treatment of relatively low-boiling oils will ordinarily produce a product superior in motor fuel characteristics, particularly with respect to its antiknock value, as compared with the motor fuel produced in the cracking unit devoted to the treatment of the relatively high-boiling oils, and it may be undesirable to blend the two motor fuel products. When flash distillation of the residual liquid from chamber 41 is desired and it is not objectionable to blend the residual liquid products from the two cracking stages of the system, the residual liquid from chamber 45 may be directed to vaporizing chamber 8, thus eliminating flash distilling chamber '14 and the communicating fractionating, condensing and collecting equipment.

Preferred operating conditions of an apparatus such as illustrated and above described may be approximately as follows: The heating coil to which the relatively low-boiling oils are supplied may utilize an outlet conversion temperature of from 900 to 1050 F., or thereabouts, preferably with a substantial superatmospheric pressure, measured at this point in the system, of from 200 to 1000 pounds, or thereabouts, per sq. in. Substantially the same or a somewhat reduced superatmospheric pressure may be employed in the succeeding reaction chamber but is preferably reduced in the vaporizing chamber to a pressure of the order of pounds, or thereabouts, to substantially atmospheric pressure. The pressures employed in the fractionating, condensing and collecting portions of the light oil cracking stage may be substantially the same or somewhat lower than the pressure employed in the vaporizing chamber. The heating coil wherein the relatively high-boiling oils are subjected to conversion may utilize an outlet temperature of the order of 800 to 950 F., preferably with a superatmospheric pressure, measured at the outlet from the heating coil, of from 100 to 500 pounds, or thereabouts, per sq. in. Substantially the same or somewhat lower pressures may be employed in the succeeding reaction chamber and may be either substantially equalized or reduced appreciably in the succeeding fractionating, condensing and collecting portions of the heavy oil cracking stage. When a separate flash distilling system is utilized for the residual liquid from the reaction chamber of the heavy oil cracking stage the flash distilling chamber employs a substantially reduced pressure relative to that employed in the reaction chamber, which may range, for example;

from 100 pounds, or thereabouts, per sq. in., down to substantially atmospheric pressure. The pressure employed in the flash distilling chamber may be either substantially equalized or somewhat reduced in the succeeding fractionating, condensing and collecting equipment.

As aspecific example of one of the many DOS",

sible operations of the process 'of the present invention as it may be practiced in an apparatus such as illustrated and above described; the charging stock is a Mid-Continent fuel oil of about 23 A. P. I. gravity which is supplied, together with high-boiling or primary reflux condensates from both cracking stages of the system, to the heating coil of the heavy oil cracking stage, wherein they are subjected to an outlet conversion temperature of approximately 930 F. and a superatmospheric pressure of approximately 300 pounds per sq. in. Substantially the same pressure is employed in the succeeding reaction chamber wherein the residual conversion products are reduced to coke. The low-boiling fractions of the reflux condensate from both cracking stages of the system, which has a boiling range of approximately 3590 to 560 F., comprises the oil supplied to the heating coil of the light oil cracking stage, wherein it is subjected to an outlet conversion temperature of approximately 975 F. at a superatmospheric pressure of about 800 pounds per sq. in. Substantially the same pressure is employed in the reaction chamber but is reduced in the succeeding vaporizing chamber to a pressure of approximately 60 pounds per sq. in. This operation may yield, per barrel of charg ing stock, a total of approximately 59 percent of motor fuel of good antiknock value, approximate- 1y 100 pounds of coke, about 5 percent of heavy liquid residue and about 600 cubic feet of rich uncondensable gas.

In an operation similar to that above described except that a separate low-boiling charging stock comprising a Pennsylvania distillate of about 42 A. P. I. gravity, approximately equivalent in volume to the heavy charging stock, is subjected to conversion in the light oil cracking stage, there may be produced, per barrel of total charging stock, about 65 percent of total motor fuel having an antiknock value equivalent to an octane number of approximately '70, about 60 pounds of coke, about 7.5 percent of heavy residual liquid suitable for use as fuel and approximately 700 cubic feet of rich uncondensable gas.

I claim as my invention:

1. A conversion process which comprises cracking hydrocarbon oil under pressure in a cracking zone, removing vapors and unvaporized oil from said zone, subjecting the vapors to primary and secondary fractionation, returning resultant pri-- mary reflux condensate to said cracking zone, cracking lighter fractions condensed by the secondary fractionation in a second cracking zone at higher temperature than the oil in the firstnamed zone, separating the resultant products into vapors and residue in a reduced pressure separating chamber, fractionating the last-mentioned vapors and separating relatively heavy and light reflux condensates therefrom, supplying the heavy and light reflux condensates thus formed respectively to the first-named zone and said second zone, introducing unvaporized oil withdrawn from. the first-named zone into a second reduced pressure chamber and therein flash distilling the same independently of said products from the second cracking zone, introducing charging oil for the process to said second chamher and distilling the same therein, removing the commingled charging oil vapors and flashed vapors from the second chamber and fractionally condensing the same to form a heavy condensate and a lighter condensate, and supplying these heavy and lighter condensates respectively to the ing zone.

2. A hydrocarbon oil conversion process which comprises cracking a relatively heavy oil in a first cracking zone, simultaneously cracking a lighter oil at higher temperature in a second cracking zone, removing vapors from said second zone and subjecting the same to primary fractionation in a primary fractionator and then to secondary fractionation in a secondary fractionator, returning reflux condensate from said secondary fractionator to the second cracking zone, removing vapors from said first zone and subjecting the same to primary and secondary fractionation independently of the first-mentioned vapors, returning reflux condensate formed by the lastmentioned primary fractionation to said first zone, introducing reflux condensate formed by the last-mentioned secondary fractionation into said primary fractionator and into contact with the vapors undergoing fractionation therein, supplying reflux condensate from said primary fractionator to said first cracking zone, withdrawing cracked unvaporized oil from said first cracking zone and flash distilling the same by pressure reduction, fractionally condensing the flashed vapors to form a relatively heavy condensate and a lighter condensate, introducing the lighter condensate into said primary fractionator and introducing the heavy condensate into contact with the vapors from the first cracking zone during the independent primary fractionation thereof, and finally condensing and collecting fractionated vapors.

3. A hydrocarbon oil conversion process which comprises cracking a relatively heavy oil in a first cracking zone, simultaneously cracking a lighter oil at higher temperature in a second cracking zone, removing vapors from said first zone and subjecting the same to primary fractionation in a primary fractionator, removing vapors from said second zone and subjecting the same to primary fractionation in an independent primary fractionator, further fractlonating the vapors uncondensed in said fractionators and supplying resultant reflux condensate to said second zone, removing cracked unvaporized oil from said first zone and flash distilling the same by pressure reduction, fractionally condensing the resultant flashed vapors to form a relatively heavy condensate and a lighter condensate, introducing the heavy condensate into the firstmentioned fractionator and the lighter condensate into said independent fractionator, supplying reflux condensate from the first-mentioned fractionator and from said independent fractionator to the first cracking zone, and finally condensing the vapors uncondensed by the further fractionation of the vapors from said primary fractionators.

JEAN DELATTRE SEGUY. 

